1. Field of the Invention
The present invention relates to an armature with a flat or plane commutator for an electric motor, especially for driving a fuel supply unit, in which the armature has a plurality of metal segments separated from each other by grooves distributed around its circumference on a front side thereof, which are connected with armature windings and which are each covered with a commutator cover at least on a front side thereof which is soldered to the respective metal segment.
2. Prior Art
This type of armature is described in European Patent Document EP 0 491 904. This armature has metal segments separated from each other by grooves distributed around the circumference on the front side. Each segment is covered on its front side with a commutator cover which is soldered with the segment. The commutator covers are separated from each other by slots which correspond to the grooves separating the segments from each other. When the covers are assembled on the armature, it must be guaranteed that the slots separating them must coincide with the grooves separating the segments so that the covers must be very exactly positioned. The slots between the covers must be formed somewhat wider than the grooves separating the segments to compensate for measurement tolerances of the segments. However the slots between the covers should be formed as small as possible because of operational considerations for the electric motor. Furthermore when the covers are soldered with the segments the solder can enter the grooves between the segments or in the slots between the covers and that can lead to a short circuit between neighboring segments or covers. During the soldering the covers are not fixed so that the covers can take incorrect positions relative to the segments.
Furthermore the side surfaces of the segments pointing in the circumferential direction are exposed, so that a deposit can be formed on the metal segments during operation of the electric motor in a corrosive media. The corrosion product formed can lead to a short circuit between the neighboring segments.